The application concerns an auditory ossicle prosthesis consisting of a bioactive material and a process for its final treatment immediately prior to and during the implantation process.
For the complete or partial reconstruction of the auditory ossicle chain, implants of various material are used. Recently, synthetic plastic materials have acquired a certain importance, because of their relatively low specific gravity and ready workability also in the intraoperative phase of the adaptation of industrially performed implants to individual conditions. In spite of the low reactivity of the implant support and the inertness of the synthetic materials, the long term success of these implants in the middle ear is not assured, as with time they penetrate the tympanic membrane.
From DE-OS No. 2 905 183 a single piece auditory ossicle prosthesis of a bioinert Al.sub.2 O.sub.3 material is known; it consists of a circular plane parallel plate with a center symmetrical straight shaft or an oblique shaft engaging eccentrically on the under side of the plate in its peripheral area, with an angle of inclination of approximately 30.degree. with respect to the normal to the plate. This known prosthesis has at least one groove in the top side of the plate, wherein if only one groove is present, the latter traverses the surface of the plate in a center symmetrical manner and if two or three parallel grooves are present, they are arranged with mirror symmetry on the circular top side of the plate. It is an essential characteristic of DE-OS No. 2 905 183 that the groove or grooves in the inclined shaft prosthesis are parallel to the plane, defined by the normal to the plate and the shaft axis.
The bioinert aluminum oxide material used induces only slight reactions in the bone tissue--wherein the thickness of the separating connective tissue layer formed may be considered a measure of biocompatibility--but as the Al.sub.2 O.sub.3 material is present in a completely inert state in the area of the middle ear, limitations concerning its long term success similar to those of the abovementioned synthetic materials must be accepted.
From "Archiv fur Ohren-, Nasen- und Kehlkopfheilkunde, Archives of Oto-Rhino-Laryngolgy", Vol. 223, No. 2-4, 1979, pp. 369-372, tympanoplastics consisting of bioactive glass ceramics are further known; they are surrounded in vivo by a 40 .mu.m thick bone layer. The configuration of the prosthessis disclosed corresponds to an excentric straight shaft arrangement, with the top side of the plate consisting of a nonplanar, spherical or ellipsoidal surface, without groove like notches.
It has been found that the implant configurations known heretofore have the disadvantage that they are not adaptable in an optimal manner to the complex middle ear anatomy and that in view of the special local conditions, they cannot be maintained stable for a long period of time. In the case of the groove orientation parallel to the plane of symmetry of an oblique shaft prosthesis known from DE-OS No. 2 905 183, there is the long term risk that in a patient exposed to unexpected strong jarring pulses particularly in the vertical direction of the human body--such as may occur during jumping, the climbing of stairs or especially during accidents, etc.--the prosthesis implanted may be "shaken" from its purely mechanical anchoring.
A further disadvantage found in the meantime consists of the fact that in many cases the surface of the plate surface has a spherical cap like configuration, leading to exposure to a nonuniform and locally strongly enhanced pressure application upon contact with the tympanic membrane. Furthermore, a groove, possibly milled in subsequently, especially when not cut center symmetrically into the lens shaped top side of the plate, offers only a relatively slight mechanical hold for the auditory meatus of the body itself, engaging said groove.